This invention relates to subcutaneously implanted injection ports, filter systems for such ports and methods of implanting such ports.
A subcutaneous injection port is a totally implantable device designed to provide repeated access to a body space such as the vascular system. Injection ports typically include an injection chamber accessible through a septum, the injection chamber being connected by an exit port and catheter to the desired body space. The device is implanted just beneath the skin, and the injection chamber may be accessed repeatedly by passing a needle through the skin and septum.
Currently marketed subcutaneous injection ports typically are top-entry devices. In a top entry device, the septum is stacked on top of the injection chamber, and the puncture surface of the septum is located parallel to the skin when implanted. The injection chamber is accessed by passing a needle through the skin perpendicular to the septum and skin. Such perpendicular access requires a relatively tall device because the injection chamber must be deep enough to accept the needle opening and the septum must be thick enough to insure a leakproof seal after repeated punctures. While such relatively tall top-entry devices are useful in certain instances in adults, they can only be scaled down a certain amount and are not so useful in pediatric patients or in particular locations in other patients where a tall device may result in tissue damage.
Another drawback of top-entry devices is that specially designed right-angle needles are usually used when long-term infusion is contemplated. The distal end of the right angle needle is inserted through the skin and septum and into the injection chamber of the top-entry device, with the proximal end of the needle lying parallel to the skin. This proximal end then is taped to the skin to secure the needle in place. These right-angle needles are known to back out of the chamber due to movements by the patient. Further, the length of the distal end of the right-angle needle must be closely matched to the depth of the implanted port. This sometimes requires trial and error of different sized needles with repeated puncture of the skin. Such repeated puncture is undesirable.
Another drawback of the top entry device is that when semi-rigid catheters are used for long-term access, special anti-kink brackets are required to allow the catheter which exits perpendicularly to the skin to be bent over and taped to the skin without kinking.
Another drawback of typical top-entry devices is that expensive non-coring needles, such as a Huber-type needle, must be used when accessing the injection chamber via the septum. The septums of such devices are relatively wide and have a short puncture length relative to the width. To allow repeated puncture, the septum must be captured under substantial compression. The compression is of a degree that a standard needle would core the septum.
Further, implanted ports sometimes flip over. Flipping is particularly likely with small devices. The overturning of the prior art top-entry devices renders their septum inaccessible.
It is desirable to use a filter in a subcutaneous injection port to prevent particles introduced into the port's chamber from entering into the body space accessed by the chamber. For example, particles of fat, skin, dust, rubber and plastic sometimes are introduced into the injection chamber of the implanted port as a needle is passed into and through the skin and septum to access the chamber. The danger to the patient from such particles is of increased concern in pediatric patients whose relatively smaller body passages may become blocked more easily than the larger passages of adults. Therefore, a pediatric injection port not only should have a low profile, but also should have a filter. However, manufacturing a filter for an injection port as small as the device of the present invention is problematic.